This invention relates to a composite NC lathe which has enabled a processing operation like that of a machining center by providing a tool spindle having an ATC (automatic tool changing device), and provides a two opposed main shaft lathe provided with a tool changeable tool spindle and tool turrets.
The directions (control axes of a NC machine) of work and cutting tool operations on a NC lathe are represented by X, Y, Z and A, B, C. A Z-axis represents the direction of main shafts, an X-axis the direction in which a tool cuts into a work and is fed, a Y-axis the direction in which the Y-axis is orthogonal to both the Z-axis and X-axis, a C-axis an angle around the Z-axis, an A-axis an angle around the X-axis, and B-axis an angle around the Y-axis.
Conventionally, a two-opposed-main-shaft and two-opposed-tool-turret lathe provided with a left main shaft and a right main shaft facing each other on the same axis and two tool turrets which are the left and right tool turrets corresponding to the respective main shafts are known (Japanese Patent Application Laid-Open Nos. 3-222012 and 8-126901). In this type of lathe, at least one of the main shafts is provided movable in the direction of the Z-axis, and a work is transferred between the left and right main shafts in accordance with a movement of a main shaft in the direction of the Z-axis. Because a work is transferred between the left and right main shafts, the processing of the work as a whole including the portion thereof which is gripped by a chuck can be carried out on the same machine.
Moreover, in this kind of lathe made capable of fixing rotary tools, such as milling cutters and drills and the like to tool turrets, the flattening, drilling and thread cutting of a circumferential surface of a work can be done by controlling the left and right of the Z-axis, the X-axis and the C-axis. This enables works of a variety of shapes to be processed throughout from a state of a raw material to that of a finished product on the same machine.
However, it is inevitable that the movable main shafts are less rigid compared with fixedly provided main shafts. Therefore, a heavy load cutting operation by a lathe having movable main shafts is restricted. Although the tool turrets are capable of changing tools in use in a short period of time, the bearing rigidity of the tools and the dimensions of usable tools are restricted because limitations are placed on support structures for the turrets and the weight and dimensions of the same.
In such a conventional lathe having two opposed main shafts and two opposed turrets, the two tool turrets are provided on the rear side of the main shafts when viewed from the side of an operator so as to maintain a work attaching to and detaching from the main shafts and to allow an operator approach the machine. Furthermore, the lathe also includes a third turret disposed on the front side of the main shafts in addition to two tool turrets disposed on the rear side of the main shafts.
A composite NC lathe provided with a single main shaft, and a single ATC-carrying tool spindle capable of controlling a B-axis and provided on a tool rest is known (Japanese Patent Application Laid-Open No. 4-283003). This kind of lathe is provided with a rotary tool such as a milling cutter and the like on the tool spindle, and capable of carrying out a processing operation of a machining center such as a process for making a large hole or flattening a diagonal surface. In this lathe, a turning process may be carried out by a turning tool which is fixed to the tool spindle in a rotation-stopped state. In this kind of composite NC lathe, only one tool spindle is fixed to the tool rest, and it is therefore possible to increase the bearing rigidity of the tools and the rotational torque imparted to the tools. This enables a heavy load cutting operation to be carried out, and large-size tools to be fixed to the tool spindle. Since many tools can be held in a tool magazine of ATC, a work can be processed by many kinds of tools. However, the ATC takes much time to change tools, and reduces a processing efficiency since a processing operation cannot be carried out when the tools are changed. When a work of an elongated shape is cut to a large depth with a tool, the work is bent due to a cutting reaction force, and a heavy load cutting operation can not be carried out.
A single-main shaft single-spindle single-turret type composite NC lathe which is a single-main shaft single-spindle type composite NC lathe added with a tool turret as mentioned above has further been provided (Japanese Patent Application Laid-Open No. 5-31601). In the lathe of this structure, a tool spindle is provided on the rear side of the main shaft when viewed from the side of an operator, and a tool turret on the front side of the main shaft.
However, when one of two tool rests is formed of an ATC-carrying tool rest with the other formed of a turret tool rest, the imbalance of processing load and processing efficiency between the turret side and the ATC side becomes large, and much time is lost due to the transfer of the tool rest and a tool changing operation of the ATC. Therefore, the processing efficiency cannot be sufficiently improved.
Due to the recent progress in technology and the diversification of demands, an increase in the kind of works and a decrease in the quantity thereof have become inevitable even at machine manufacturing sites. Moreover, the labor saving and the improvement of the productivity have been on demand. In order to meet such requirements, it is necessary to process works of various shapes in a state of raw material into finished products efficiently on the same machine. In the present invention, it is unnecessary to make an arrangement for changing the kind of the machine in use when the operation for transferring works between many kinds of machines and the kind of works are changed. Moreover, a loss of time during the processing operation is avoided, and the heavy load cutting of a work becomes possible. This enables many kinds of works to be processed continuously in an unmanned condition with a high efficiency.
The composite NC lathe according to the present invention is provided with a left main shaft 1L and a right main shaft 1R facing each other on the same axis, a left turret tool rest 8L and a right turret tool rest 8R positioned on the lower front side of the main shafts 1L, 1R, when viewed from the side of an operator, a third tool rest 6 positioned on the upper rear side of the main shafts 1L, 1R when viewed from the side of the operator, a tool magazine 19 holding tools to be fixed to the third tool rest, and an automatic tool changing device 20 for these tools. The left turret tool rest 8L and right turret tool rest 8R are provided with tool turrets 9L, 9R respectively on which many tools can be fixed. The third tool rest 6 is provided with a tool spindle 14 directed toward a work. The left main shaft 1L and right main shaft 1R are connected to main shaft motors 4L, 4R that can control C-axis and can be driven independently or synchronously. The movement of the third tool rest 6 can be set in the directions of the Z-axis, X-axis and Y-axis. The tool spindle 14 is provided on the tool rest 6. Furthermore, the tool spindle 14 is capable of controlling the position in the direction the B-axis and fixing the position.
When the composite NC lathe according to the present invention is used, the processing of a work can be continued by simultaneous operations of the left turret tool rest and right turret tool rest even while the tools are changed on the third tool rest (which will hereinafter be referred to as xe2x80x9ccomposite tool restxe2x80x9d) 6 provided with the ATC-carrying tool spindle 14. Only a special processing operation and a heavy-load processing operation which cannot be carried out on the turret tool rests may be carried out on the composite tool rest. Therefore, it is possible to minimize the influence which a tool changing operation of the composite tool rest and the transfer time of the tool rest exert on decreasing the processing efficiency, and a processing cycle time can be improved.
In the processing of a bar material in which both end portions of an elongated work are gripped by the left main shaft and right main shaft, a balanced cutting operation can be carried out by a composite tool rest of a large cutting reaction force and two turret tool rests of a small cutting reaction force. Namely, a heavy load cutting operation not accompanied by the flexure of the work can be carried out, and a further improvement of the processing efficiency can be attained.
When the left main shaft 1L is provided fixedly in the structure according to this invention, it is possible to improve the bearing rigidity of a work in the processing work in a first step, and to simplify a method of supplying a bar material through a central hole of the left main shaft. When the right main shaft 1R is provided so that this shaft can be moved in the direction of the Z-axis, the transfer of a work between the left main shaft and right main shaft can be carried out. When a locking device for mechanically stopping the movement of the right main shaft in the direction of the Z-axis is provided, the rigidity of the right main shaft during a heavy load cutting operation can be heightened.
When both the left and right tool turrets 9L, 9R are provided so that they can be moved in the direction of the Z-axis and the direction of the X-axis, it is possible to carry out a simultaneous processing operation using an arbitrary combination of the composite tool rest and two turret tool rests. In this case, when the left and right tool turrets 9L, 9R are rendered movable from a position in which the left main shaft is opposite to a work to a position in which the right main shaft is opposite to the work, it is possible to freely combine the left and right main shafts and tool turrets, and the kind of the tools usable for the processing operation on each side can be increased.
When the tool turrets 9L, 9R are formed so that rotary tools can be fixed thereto, it is possible to process a work stopped by the rotary tools on the turrets simultaneously with a milling process applied to the work on the composite tool rest.
When the tool turrets 9L, 9R are fixed to the portions of the respective tool rests 8L, 8R which are close to the opposite tool rests, the tools on the two tool turrets can be brought close to each other. Therefore, the processing of the work gripped by one main shaft can be done easily by using the two tool turrets.